Amino acid sequences of a number of antibodies specific for type III and VII pneumococcal polysaccharides will be determined. While most attention would be directed at variable and hypervariable region sequences, in several instances complete sequences of the antibody molecule will be obtained in order to either correct existing constant region sequences or to determine allotype-related sequences. BIBLIOGRAPHIC REFERENCES: Rosemblatt, M.S., Margolies, M.N., Cannon, L.E., and Haber, E.: Peptides: An analytical method for their resolution by polyacrylamide gel electrophoresis applicable to a wide range of sizes and solubilities. Anal. Biochem. 65:321, 1975. Brauer, A.W., Margolies, M.N., and Haber, E.: The application of 0.1 M Quadrol to the microsequence of proteins and the sequence of tryptic peptides. Biochemistry 14:3029-3035, 1975.